forming words with the correct letters in the correct order, or the ability to do this

He's hopeless at spelling. 他的拼写简直糟透了。

My computer has a program which corrects my spelling. 我的计算机有纠正拼写错误的程序。

Your essay is full of spelling mistakes/errors. 你的文章里通篇都是拼写错误。

the way a particular word is spelled

This dictionary includes both British and American spellings of words. 本词典兼收单词的英国和美国拼法。